The present invention relates to the field of data communications, and in particular to the provision of information to a portable or other mobile device such as a mobile telephone, a lap-top or palm-sized data processing device, a data processing system integrated within a vehicle, or any other mobile receiver device.
Currently, solutions for providing information for route planning and associated tourist guides are delivered as static databases to work with an application (e.g. Microsoft AutoMap), usually on a CD-ROM. The main disadvantages of such solutions are that the finite space of the storage medium restricts the scale of the information and, being static, the information is inherently dated. The storage capacity issue is being worked on by Matsushita Communication Industrial Co., Ltd. and others, but this and the lack of currency of information remain significant issues especially for supplementary data such as hotel guides and services information which is associated with a map.
Alternative solutions which provide a dynamic solution are typically based on the World Wide Web Internet service. Since the information held on a Web server computer can be updated whenever appropriate, it is possible to ensure that the information accessed by end users via their Web Browsers is current. However, such solutions require the user to either download the pertinent information to their laptop or other portable device before leaving on a journey, or having to browse the information over an expensive dialup service to the Internet during the journey.
UK patent application GB-A-2195868 proposed an alternative solution in which a plurality of transmitters, located in different regions and broadcasting on different frequencies, each broadcast map information relating to their respective regions. Portable receivers are able to receive broadcasts from any of the transmitters and are able to display a map generated from the broadcast information.
Significant problems with the solution suggested in GB-A-2195868, and with many other dynamic solutions, include the problems inherent in currently available wireless communications of potential failures to receive a complete transmission. Such failures may occur for example because the mobile device is temporarily shielded during receipt of a transmission, such as when a user drives into a tunnel, or because the mobile device moves out of the range of the transmitter during receipt of a transmission. Also, the mobile device may be switched off during receipt of a transmission. These problems are emphasized by the typically large amount of geographic information which has to be successfully transmitted in order to give reasonable map detail, since this is relevant to both the likelihood of a failure before transfer is complete and the time required for retransmission.
Matsushita Electric Industrial Co., Ltd. has announced development of a map processing technology which automatically processes maps into a simplified form before they are transmitted to a PDA. The simplified maps have a reduced data size compared with the original maps and so can be transmitted more quickly as well as being easier to read on PDA screens. Although such a solution increases the likelihood of map data being transferred before a communication failure occurs and reduces the transfer time, the Matsushita map reduction solution does not solve the problems of communication failures which occur during a data transfer.
Additional disclosures of map broadcasting solutions which suffer from the above-described problems of communication failures can be found in Japanese patent application JP6229768 (which describes FM broadcasting of map data and uses a position detector, superimposing the vehicle position on a map image generated from the broadcast data) and JP8201085 (which describes a navigation system implementing a method for reducing the requirement for switching of FM broadcasting stations by selecting an optimal FM broadcasting station for a recommended route to a destination). Additionally, French patent application FR2742565 discloses data being broadcast by digital radio and then being filtered on receipt to extract information relevant to the current zone in which a vehicle is located.
The present invention provides methods and apparatus for broadcast of geographic information to mobile devices, in which the information is organised for transmission as a plurality of data elements which each relate to and include an identification of a particular segment or region of a map. Positions on the map can be defined with reference to segments or regions. For the purposes of data transmission, the data elements are treated as independent of each other.
xe2x80x9cGeographic informationxe2x80x9d in this context includes map and route information and any information which has a geographic relevance such as weather, traffic and local services information.
The data elements each include a map reference which is sufficient to uniquely locate them in a map. This independent self-identification of map location within each data element ensures that the data elements can be transmitted and received independently of each other and received elements can then be processed at the mobile device to build up a meaningful representation of received geographic information even if one or more of the transmitted data elements is not received. Thus, the present invention is more robust than an xe2x80x9call or nothingxe2x80x9d approach to broadcasting of geographic information.
With independence between data elements during transmission, there is no constraint on the order in which data elements are received. A preferred embodiment of the invention broadcasts the geographic data as a data carousel, with each data element being retransmitted periodically (i.e. similar to broadcast of TeleText information). This supports filling in of gaps in a map. Geographic information within a data element for which receipt initially fails but which is successfully received on retransmission can be inserted into the appropriate place in the map.
In a first aspect, the invention provides a method of distribution of geographic information to mobile devices via a wireless communications network, the method including: generating a plurality of data elements to contain the geographic information, each data element relating to and including an identifier of a specific single segment of a segmented map; and broadcasting the data elements via the wireless communications network for receipt by the mobile devices.
In a second aspect, the invention provides a data processing system for generation of data elements containing geographic information, for distribution to mobile devices, the data processing system including a data processing component for separating input geographic information into data components which are each related to a single segment of a map, in accordance with a defined map segmentation, and combining one or more of the data components related to a specific map segment with an identifier of the specific map segment to create a data element.
In a third aspect, the invention provides a wireless data communications network for transmission of geographic information from a first data processing system to mobile devices, the network comprising: a first data processing system including means for generating a plurality of data elements to contain the geographic information, each data element relating to and including an identifier of a specific single segment of a segmented map, and means for distributing the data elements via the network to a plurality of geographically distributed transmitters; and a plurality of transmitters for broadcasting the data elements via wireless communications for receipt by the mobile devices.
In a fourth aspect, the invention provides a mobile data communication and data processing device including: a receiver for receiving wireless broadcast transmissions including receiving data elements which each include geographic information related to a specific single segment of a segmented map and an identifier of said map segment; a memory for storing a representation of the segmented map; a processing component implementing functions to process the map segment identifier of a received data element to determine which segment of a map the geographic information included in the data element relates to, and for adding the geographic information of the data element to the respective segment of the segmented map representation within the mobile data receiver device. The functions implemented by the processing component provide the capability to process a plurality of received data elements which may be received in any order, and to add the geographic information of the received data elements to the respective segments of the segmented map representation to build up a map over time.
In a fifth aspect, the invention provides a method for building a map representation on a mobile communication device, including the steps of: receiving broadcast wireless transmissions including receiving data elements which each include geographic information related to a specific single segment of a segmented map and an identifier of said map segment; storing a representation of the segmented map; processing the map segment identifier of a received data element to determine which segment of a map the geographic information included in the data element relates to; and adding the geographic information of the data element to the respective segment of the segmented map representation within the mobile device.
In the presentation of received data elements, a visual indication may be provided of whether all data elements relevant to a particular map segment have been successfully received, such as by showing incomplete segments in xe2x80x9cgreyed outxe2x80x9d style or with some other visual emphasis. This can be implemented simply, for example by recording at the transmission apparatus how many data elements are relevant to each segment and then checking at the receiving device how many received data elements include the map reference for that segmentxe2x80x94where there is a mismatch, the displayed information is greyed out.
In a preferred embodiment of the invention, data is transmitted for receipt by the mobile devices as a plurality of separate broadcast data streams, such as on a plurality of different communication channels. A channel in this context is a particular operating frequency band and associated transmission parameters, or a timeslot within a frequency band). The plurality of channels preferably include a low level of detail (LLoD) channel and one or more high level of detail (HLoD) channels. The data elements sent via the LLoD channel provide a basic map outline and major features, whereas the data elements of the HLoD channels provide finer resolution information supplementary to the LLoD channel. The data elements sent via the LLoD channel typically include only a small number of bytes of information (for example, 5 or 10 bytes). This enables an overall picture to be built up quickly. The HLoD data elements may be considerably larger (for example, 50 bytes), with successful receipt of the HLoD data elements enabling a detailed picture to be built up. Alternatively, the HLoD data elements may be small but the map segment size relevant to their information content may be smaller than for LLoD data elements.
As noted above, in certain embodiments of the invention the geographic data is transmitted as a data carousel with periodic retransmission of each data element. In such an embodiment, the LLoD data elements may be retransmitted more frequently than HLoD data elements, so that there is a higher likelihood of LLoD data elements being received within a time period acceptable to users. This can be independent of whether or not the LLoD and HLoD data elements differ in size or map segment size, but a smaller number or smaller size of data elements on a LLoD channel further improves the likelihood of successful receipt within an acceptable timescale.
According to the preferred embodiment of the invention, when a receiving device starts to receive it will receive data elements related to the local area of its current location, identify the relevant map segments of its internal map structure and start to fill in the segments to build up a map.
In one embodiment of the invention, a receiving device is able to identify when a data element has failed to arrive which is relevant to the map segment in which the receiving device is currently located. For example, this may use GPS or an alternative to determine the location of the receiving device and could use the previously described check of expected numbers of data elements. Alternatively, the check may comprise simply identifying data segments for which no data element has been received. Having identified failure of one or more local data elements, the receiving device concentrates its resources on the communication channel relevant to the missing data element or on the LLoD channel to try to obtain at least the LLoD data element or elements for that segment. It should be noted that a receiving device may receive on multiple channels simultaneously or alternately, and may be receiving from one or a plurality of transmitters.
In addition to each data element including information for identifying the location of the relevant map segment such that data elements can be transmitted as independent elements, the content of each data element is preferably organised into a plurality of independent components. xe2x80x9cIndependentxe2x80x9d in this context does not mean that their information is not related to each other, but rather that the transmission of each component and its interpretation by the receiving device is not dependent on other components.
This embodiment of the invention is preferably implemented by including data component delimiters within the transmitted data stream. If a communication failure occurs, it is then possible to determine which components were successfully received and to process the successfully received components at the mobile device rather than having to treat the whole data element as failed.
The data element components are preferably ordered within a data element such that the more significant components are at the beginning of the data element.
In a further embodiment of the present invention, there is provided a solution combining static provision of geographic information (such as on a CD-ROM or DVD-ROM) with dynamic updates to the static information. Updates since the latest distribution of a static database of geographic information are transmitted as described above and the receiving device superimposes the received update information on the map grid. This involves transmission of significantly less data than if the complete map data is transmitted, while still achieving the currency of local data which is achievable by fully dynamic solutions.
The broadcasting of geographic data according to the invention is preferably a digital wireless broadcast which can be received by any receiver device within the vicinity of a transmitter, but it may also be an interactive broadcast where the receiving devices can influence the content or other characteristics of the broadcast, or a transmission to specific user groups.